The instant invention generally relates to a purification and odor-control system for wastewater or liquid containment areas.
Recent attention has focused on the need for environmental control in and around manure lagoons. Odors resulting from many manure lagoons and containment areas significantly detract from the use, enjoyment, and value of surrounding property. The formation of a manure crust seals the containment area thereby preventing natural aeration and contributing to an unbalanced anaerobic state. In fact, in colder climates, the formation of an ice cap over the crust acts to further seal the lagoon and creates a greenhouse effect. The spring thaw results in an acute and malodorous release of methane, hydrogen sulfide, and other gases. The formation of the crust also creates a breeding ground for flies, believed to be the primary disease vector from the farm to the surrounding community. Birds, in turn, often feed on the fly larvae and constitute a secondary disease vector. Crust formation also seals the lagoon from aerobic replenishment, and therefore contributes to an anaerobic state in the lagoon wherein odoriferous compounds are maximized. Finally, crust formation also inhibits slurry removal thereby contributing to an inoperable lagoon. The benefits of odor control and crust prevention thus become obvious.
Economic and political pressures are now encouraging the development of pig farms, in lieu of tobacco farms for example. Recent developments however, have restricted the design of new or expanding pig farms. Concerns such as odor, air quality, and ground and surface water quality, often implicating the Clean Water Act and/or the Clean Air Act, drive the restrictions.
In fact, a recent U.S. Senate study details the magnitude of environmental problems caused by animal waste. The findings indicate that the amount of animal manure produced annually is conservatively estimated to be 130 times greater than the amount of human waste produced. Stated another way, a 50,000 acre farm in Utah has been cited as potentially producing more waste than the entire city of Los Angeles. Other findings indicate that agricultural officials consider 60% of rivers and streams xe2x80x9cimpairedxe2x80x9d, with agricultural runoff the largest contributor to the pollution. Anecdotally, a 30,000 fish kill resulted from a weekend hog manure spill in Iowa. Efforts are therefore currently underway to impose national standards on livestock producers.
On a state level, certain areas such as North Carolina have enacted moratoriums on new or expanding hog farms. North Carolina has also granted counties zoning control over farms with more than 5,000 hogs. Industry experts warn that as more restrictions are placed on U.S. hog farms, pork production could move to other countries thereby damaging family farms and sending food profits overseas. The net result of further restrictions limits the land use and therefore detracts from the profitability of the farmland.
Aside from the private and public nuisance concerns, acute odors also indicate the potential for disease and reduced hog propagation due to respiratory problems, for example. In humans, even lower concentrations (100-300 parts per billion) of gases such as hydrogen sulfide are known to cause eye irritation, headaches, diarrhea, nausea, and an inability to sleep. Many of the gases, bacteria, viruses, spores, and worms found in manure contribute to a number of illnesses that may inhibit the full maturation of the swine, result in condemnation of all or part of the pig, and/or result in their premature deaths. In addition, many pathogens harmful to animals may also be harmful to workers. The swine flu and xe2x80x9cfarmer""s lungxe2x80x9d are illustrative. It is believed that insects and birds transfer these pathogens to the surrounding community.
In general, hog manure and urine contains or evolves into ammonia, hydrogen sulfide, methane, nitrates, trihalomethanes, spores of molds, and other contaminants. Research has shown that animal effluvia and the putrefactive gases resulting from animal and vegetable tissue are generally present in and around hog barns. Putrefaction produces highly odorous gases and compounds such as ammonia, amino acids, aromatic fatty acids, metabolites, mercaptans, indole, skatole, cresol, and alkaloid-like ptomaines such as tetramethylene-diamine and pentamethylene-diamine.
Several methods of storage and/or disposal include above-ground slurry storage, below-ground slurry storage, anaerobic lagoons with or without cover, aerated lagoons, oxidation ditches, and solid/liquid separation. Each method has its advantages and disadvantages.
Slurry storages are comparatively very costly, but the added cost is often the least risk option for farmers because slurry storages guard against mechanical and human failures that could result in environmental concerns. Straw covers are sometimes used in an effort to control odors. Other materials such as macadamia husks, cornstalks, plastic, peat moss, foam, and leka rock may also be used to cover the storage areas. The cost increases depending on the material. Additionally, temperature, humidity and light intensity can adversely effect the performance of biocovers such as straw and cornstalks. Covers may mask but do not eliminate the odors, however, and furthermore they do little, if anything, to eliminate or reduce the fly population.
A common misconception is that covers control odors. Covers actually promote poor lagoon health because there is little or no air for aerobic activity. Therefore, the odors associated with the liquid will actually increase over time. The anaerobic activity in a covered lagoon is increased for awhile, but in an unbalanced state (i.e. oxygen and aerobe deficient), the lagoon can quickly become unstable resulting in very poor organic treatment (i.e. solids buildup). Other problems associated with covered lagoons are confined explosive and toxic gases beneath the cover which must be vented, unhealthy recycle water (to the barn flushing system) that contains foul gases and higher pathogenic loads, and poor solids treatment capacity. Nevertheless, where covers are still desired, the disadvantages stated above drive improvements in the control of covered containment areas.
In the same way, odors, crust formation, and flies also plague anaerobic and aerobic lagoons open to the environment. Alternatively, the use of oxidation ditches and liquid/solid separation processes are significantly more costly as compared to other waste management methods.
Scientists have attempted to reduce odors from the annual spring runoff into the North Saskatchewan River at Edmonton, Alberta. The odors have been characterized as septic, manure, musty, earthy, and hay-like. Despite oxidative treatment, the odors persisted thereby supporting the scientists"" belief of the futility of relying strictly on oxidative treatment. Other odor control methods have incorporated aeration with costly additives to control the odors.
Other efforts are underway to reduce or eliminate manure odors. For example, the University of Minnesota Agricultural Engineering department recently began a project to measure, chart, and record odors emitted from different livestock production sites around Minnesota. As one engineer states, there is currently very limited knowledge about the odor from hog production systems. The main thrust of the project is to develop a database to assist communities and pork producers in developing reasonable expectations about odor. At the national Center for Agricultural Utilization Research in Peoria, Ill., researchers sought one million dollars to attack the malodorous nature of manure. Other problems tabled for action include air and groundwater quality.
The use of ozone is well known as a disinfectant or sterilizing agent. In general, due to its disinfecting properties, ozone has not been considered a viable or feasible alternative when treating manure pits or lagoons. The conventional wisdom is that disinfection caused by the use of ozone would interfere with the microbiological balance required for organic digestion.
The following references are herein incorporated by reference.
In the article entitled, xe2x80x9cEVALUATION OF ODOUR REMOVAL BY PILOT-SCALE BIOLOGICAL TREATMENT PROCESS TRAINS DURING SPRING RUNOFF IN AN ICE-COVERED RIVERxe2x80x9d, Wat. Sci. Tech. Vol. 31, No. 11, pp. 195-201, (1995) S. E. Hrudley, P. M. Huck, M. J. Mitton, and S. L. Kenefick teach biological treatment of runoff water having a strong odor characterized as septic, manure, musty, earthy, and hay-like. Biological treatment using granular activated carbon can produce an essentially odor-free effluent during a transient raw-water odor event. On the other hand, for odor reduction the scientists teach the futility of relying on a strictly oxidative treatment such as ozone.
U.S. Pat. No. 3,960,718 to Lebo teaches the use of ozone as a sterilizing agent in sewage treatment.
U.S. Pat. No. 5,298,198 to LaCrosse teaches the purification of wastewater from a swine manure pond through an aerator at relatively low flow rates and pressures.
U.S. Pat. No. 3,884,804 to Robinson et al. teaches the use of xe2x80x9cContacogenxe2x80x9d particles comprising solid catalyst portions having hydrophobic surface portions, wherein the particles are floated on the surface of a slurry of animal wastes. The particles promote the oxidation by air of the odoriferous compounds produced by the degenerative breakdown of the animal wastes.
U.S. Pat. No. 5,656,246 to Patapoff et al. teaches a wastewater treatment process incorporating ozone as a sterilizing agent, and oxidation technology. The waste must be transported to the reactor from the normal collection areas.
U.S. Pat. No. 5,053,140 to Hurst teaches a method for food process water purification utilizing ozonation. Ozone is clearly taught as destructive to bacteria.
U.S. Pat. No. 5,290,451 to Koster et al. teaches a liquid manure treatment process incorporating an aerated reactor, a denitrification reactor, a liquid/solid separator, and sedimentation tanks. The waste must be transferred to the process from the normal collection areas.
U.S. Pat. No. 5,616,163 to Halfter teaches a liquid manure treatment process incorporating aeration as a method of stripping odorous substances.
U.S. Pat. No. 5,053,140 to Hurst teaches a method for food process water purification utilizing ozonation.
Despite ongoing efforts, there is still a need for a cost-effective system that reduces or eliminates manure odors and if necessary, further prevents manure crust formation thereby eliminating a primary breeding ground for the insect/fly population. Given the moratorium on hog production due to ongoing environmental concerns, it becomes quite clear that methods of control such as simple aeration and/or covering the smell through covers or pit additives, for example, simply do not achieve the necessary odor and solids control required.
The aforementioned problems are solved by a liquid treatment system that ozonates an upper stratum of liquid contained in a liquid container. More specifically, an upper stratum of a liquid volume is preferably ozonated while maintaining anaerobic conditions in a lower stratum. This permits anaerobic digestion of manure waste, for example, while still eliminating the odoriferous gases through oxidation in the ozonated upper stratum.
Accordingly, an object of the present invention is to deodorize and oxidize odoriferous compounds within any given liquid in a liquid containment area.
Another object of the present invention is to deodorize the manure slurry within a liquid manure container such as a pit or lagoon.
Another object of the present invention is to eliminate or reduce the indigenous fly population around any liquid waste containment area.
Another object of the present invention is to deodorize and disinfect the air within a covered liquid containment area.
Yet another object of the present invention is to prevent manure crust formation in a manure lagoon and eliminate a fly breeding ground, thereby further eliminating a primary disease vector from the farm to the community.
In accordance with these and other objects, the present invention oxidizes gases naturally associated and produced with aqueous and/or oily/fatty liquid wastes, and also those gases resulting from the bacteriological breakdown of the wastes. The injection of ozone into the contaminated fluids deodorizes and disinfects thereby effectively controlling the odors emitted therefrom.
In a first embodiment, a perforated tube or plurality of perforated tubes extends across a lagoon within an upper portion of the total volume, most preferably in the upper fourth portion of the total volume. When ozone is pumped into the perforated tubing, the gas is evenly dispersed through an upper portion of the liquid that approximates one fourth of the total volume. The odoriferous gases thus contact the ozone and are oxidized prior to their release into the atmosphere.
In a second embodiment, the first embodiment described above may also contain a cover, polymeric for example, over the liquid container. A perforated tube or a perforated plurality of tubes may then, if desired, be extended above the liquid container but within the air-gap of the covered area, thereby further oxidizing any odoriferous gases that may have escaped the ongoing slurry oxidative treatment.
In a third embodiment, a buoyant vehicle is randomly preferably propelled across the surface of the liquid by electrical propulsion. A preferred embodiment contains an electrically actuated pump thereby providing a propulsion means for propelling the vehicle across the surface of the lagoon. Ozone is diffused into the slurry by way of a gas injector. The ozone and electrical power are preferably introduced at or near the bottom of the lagoon or pit. Ozone functions as a powerful oxidant that virtually eliminates the odors by maintaining an aerobic/anaerobic balance in the manure slurry. The random movement of the buoyant vehicle creates an ozonated xe2x80x9ccapxe2x80x9d or oxidation zone in about the upper quarter of the slurry container, thereby eliminating the odor causing gases prior to their release into the atmosphere. Concurrently, an anaerobic state persists below the xe2x80x9ccapxe2x80x9d thereby permitting anaerobic digestion of the manure. The vehicle is also heavy enough to fragment any floating masses of crust that typically form in manure lagoons, for example, and ice thereby eliminating the fly breeding ground and also further inhibiting an anaerobic state and acute odors in the liquid. If a cover is desired, ozonation of the resultant air-gap over the liquid container may be accomplished as described in the second embodiment.